I need help to recover my contacts and photos from my last backup

In order to restore from a back up you would need to go to Settings>General>Reset>Erase all content and settings

when your phone restarts you will have to go through the device set up and sign into your iCloud with you existing Apple ID and choose the back up you wish to restore from.

An iPhone backup does not allow you to pick and choose what items to restore. It's pretty much an all or nothing restore. Contacts and Photos are part of iCloud and are not included in the backup. Follow the directions given above.